The incident took place at dawn when gunmen attacked the army base at the village of Ain al-Jahash near the city of Hamam al- Alil, some 20 km south of the provincial capital city of Mosul, the source told Xinhua on condition of anonymity.

Hours later, reinforcement troops arrived at the site and found the bodies of the soldiers, which were all beheaded by the gunmen, the source said.

The Sunni-majority Nineveh province and its capital Mosul, some 400 km north of Baghdad, has long been a stronghold for insurgent groups, including al-Qaida militants, since the U.S.-led invasion of Iraq in 2003.

Iraq is witnessing its worst violence in recent years. According to the UN Assistance Mission for Iraq, a total of 8,868 Iraqis, including 7,818 civilians and civilian police personnel, were killed in 2013, the highest annual death toll in years.